In radio communications system of today the number of radio access technologies are continuously increased and to serve as many user equipment as possible it is important to support different radio access technologies. Modern radio base stations may be equipped with support for several radio access technologies. For an operator of a radio communications system, this kind of multi Radio Access Technology (RAT) radio base station means that the operator only need to buy one radio base station in order to cover an area with different RATs, such as, Long Term Evolution (LTE), LTE-Advanced, 3rd Generation Partnership Project (3GPP) Wideband Code Division Multiple Access (WCDMA) system, High Speed Access Data (HSPA), Global System for Mobile communications/Enhanced Data rate for GSM Evolution (GSM/EDGE), Worldwide Interoperability for Microwave Access (WiMax), Ultra Mobile Broadband (UMB), and/or the like.
A multi RAT radio base station, that is, a radio base station that serves a plurality of cells of different RATs, may be designed in many different ways. For example, radio units, such as antennas, used for each RAT may be separated or common in the radio base station. Multi RAT radio base stations of today are statically configured. This means that the resource split between RATs may not be changed. A multi RAT radio base station may comprise a Radio Resource Manager (RRM) that may be used to move a User Equipment (UE) between different RATS with set frequency ranges, for example, for the purpose of load balancing. However, this is inefficient since UEs may be forced to use a less advanced RAT than what the UEs are capable of, leading to an inefficient use of resources within the radio communications network.